Tide calculator



All muz uzmw Dec. 23, 1952 H. E. L. OWEN ET AL TIDE CALCULATOR FiledDec. 17, 1948 F IG. l

Vum" wA-rsA oqplARv SPRING TIDE Dec. 23, 1952 Filed Dec.

' Dec. 23, 1952 H. E. l.. OWEN ETAL 2,622,8,00

TIDE CALCULATOR Filed De. i7, '1948 4 sheets-sheet 5 DMW @ma Attorneys-DeC- 23, 1952 H. E. l.-.OWEN ET AL 2,622,800

TIDE cAmULATor'a 'I Filed Dec. 1'7, 1948 4 Sheets-Sheet 4 Patented Dec.23, 1952 on, England, assiignors "to' Tidak Application December 17,1948, Serial No. 65,7%-

' """I Gleatlritain December 19, 1947 eine www@ This invention relatesto.devcsforevaluation ofL data relating to tides and.' in particular, toa devicel for-v evaluating. the. heightgoff tide water at anygiren time.Devices ot. this nature haveprey viouslyheenused but they vall involveeither fairly extensive calculation or; fairly extensive draft,-lfzfianship` before the user can, be given the depth of. water. This isinformation which is indispensable to the navigator. and Which lie. musibe able to determine for himself veryrapidly.`

The device in accordance with theL invention enables s uch evaluationsto be. made by means, which involve thevery. minimum of calculation.Indeed, the.Y only calculation which is required in order to determinethe, depth of; watery is to add to an amount determined by setting the,device, the depth of water at low. water ordinary, spring tide which isascrtainable. from chart-s or, nautif cal tables and is -generallyvreferred' toV as the sounding. v

The invention will be explained by reference to* the accompanyingdrawings in which:

Fig. l is a diagram for.k elucidating various technical terms usedfheein;

2-` is a schematic representation for the principle underlying' theconstruction and use of the device oi the invention;

ijig'. 3 is a front view of a preferred embodiment oi an instrument inaccordance'withth'e invention;

Fig, 4 is a rear View of said instrument;

Fig. 5 perspective viewof'part of Eig. 3 withiceitain p'artsfshownbroken away;

Fig. 5 a section taken bn the lin'VI-VI in I ig. 'l' is-l a" schematicrepresentation oi a modined iorndfoi the instrumentfshovv-i in Figs'S-G.

in order Vthat the terms used'heijein in relation to tides may' beunquestionably"understood, they will he explained with referenceto"Figure 1 of the accompanying drawings; 'v

I iiefdiiirenoe'ivn" Ievelfat High Water and at Low Water'for 'anyyparticilar tide isknown as einer 'lheranlge the high and low waterlevels vary cyclicallyY 'with' the'phases" 'of the moon. 'ljhey alsovrvary with local'onditins'such as wind 'barqmetic tending s. "The"highest and ,gtensivetides'mare'known as Spring Tides and, where the n"iecto'1'local conditions' is neelected, they arev referred to asOrdinaryy Spring @dest l t, .l

N tical tahles usually give data in connection with tidesinrelatlio'n'mto allia'tmvel which can he at any arbitrary levely but'is 'generally 2 clicsen as that of LW..Wa ter at Ordinary Spring` Tide.v'lpfhefdepth'if the' oceanbedfbelow the Datein isfknwii asy thesounding. The height abovevthe Datum t'which'the water rises at anyparticular tide knowias the Height cwi/Tide Qrthemse. A

Clearly, if the Datum coincides with Low Water Ordinary Spring Tide, theSpring Range and, the Spring Rise ereequal It will clear'rom aninspection of Fig. l, thev difference between the SpringiRise andthedaysfI-Ieight of 'Ifideis the vsamelasthe difference between High WaterOrdinaryspring Tide and High Water for theftidein'question and,ytherefore, also as the difieence between Loti/ Water and theDaturnlevelf"y f Any particular tide rises and falls at the same overallrate but the rate varies from 'moment to moment during the, period ofthe tide; Change in water level cannjot le, 4expressed as a linearfunctionl oi time; itis more'nearly na' simple harmoniofiurliwf tmef A'4 i Fig 2l 0f @e EPQCQmP'mYPg @FW/ings is. af da' gram showing theprinciple upon which the construction of the'devices in accordance withAthe inventionishased.

A is a chart, having two parallel scales al, a2. The line B is drawnfrom a point'on'the lscale a1 representing LOW Weit fQI a peltculaf Gidet0 e peint on in@4 Stale. it repreiiig'ligh Water for that tide,

Cl is. a. time lis. Semi-,Circuler edgev C1 is divided linearly torepresent equal intervals during, the duration ofthe tide. I tslstraight edge ci is divided by. dropping on toV it perpendiculais fromthe. divisiOnsiQf; the edge 0.1 and there" fore, forms a simple harmonictime scale.

D is e weer the edge d 0f which iS. divided similarly to the scales ofand a2 and which can be moved across parallel. t0. 15h05@ s'eSf K Thelline DL joining the zero points on the scales ai; ai and d representsthe. Datum lille- From the explanations given. attive, it should beclear that in any position of the cursor D, its scale d wiiiheintersected by the 1in@ i3, ai a point which will indicate theY heightof water above Datum at the time indicated by. the intere section of thescale c? by the cursor. Therefore, by Setting the cursor at particulartime C11 the scale c2, the height of water at that time (which is theinformation generally reqnired, by the mariner) will be given on thescaleA d.

If; as was done abovejthe left hand scale al is used as the Low,Tx-'vater scale and the scale a2 as the High Water scale, 'thetirnescale C will 3 have its zero at the left hand side for a rising tide andat the right hand side for a falling tide. Thus, the time scale C isread from left to right or from right to left according as the tide isrising or falling.

Alternatively, the scale Ll can be used as the low Water scale for arising tide and the high water scale for a falling tide, in which case,the time scale, Will always be read from left to right.

Figs. 3-6 of the accompanying drawings show a practical embodiment of aninstrument based on the principle explained in connection with Fig. 2.

The instrument has a frame I0 Within which is fixed a panel C on whichare marked a series of time scales c2.

The time taken by a tide to fall and to rise varies in different partsof the world from 4 to 8 hours. 'I'he panel C has a number of horizontalscales c2 all of the same length and representing tide durations of from4 hours to 8 hours at 20- minute intervals. Each of the scales c2 isharmonically divided by the method explained in connection With Fig. 2as to give indications of ZO-minute time intervals over the duration ofthe tides.

Within the frame I0 below the panel C is a pointer I2 having a line B onit which corresponds to the line B of Fig. 2. This pointer is carried bya plate I4 mounted to slide up and down on the base I6 of theinstrument. Its pivotal axis I8 lies on the line B and midway along itslength. A spring I9 carried by the plate I4 urges the pointer clockwiseso vthat it rests on a pin 20 on a plate 22 mounted to slide up and downon the base I6.

The plate I4 is attached to a rod 23 which lies in a guide slot 24 inthe base i6 and has a pin 25 which projects out through a slot 26 in thebase. The plate 22 is similarly attached to a rod 21 which lies in aguide slot 28 in the base and has a pin 28 which projects out through aslot 30 in the base. Thus by moving the plate I4 by means of the pin 25,the pointer I2 can be moved bodily up and down and by moving the plate22 by means of the pin 29, the pointer can be swung about its pivot.

A cursor D is also provided which is mounted to slide across the base I6. It has an upper part 32 and a lower part 34 attached to a member 36which is mounted to slide across the base I6 on a fixed rod 38. Theupper part 32 is transparent and has a line 40 scribed on it; the lowerpart 34 is in the form of a straight edge aligned with the line 40 andis provided with a scale which corresponds to the scale d of Fig. 2.

The frame has a back cover plate 42 on the inside of which is mounted aneccentric 44. The shaft 46 of the eccentric has iixed to it a largewheel 48 having a milled edge which projects beyond the frame work. Theeccentric is connected to the cursor D by means oi' a, connecting member49 which is pivotally mounted on the base at 50, has a forked upper end52 which embraces a pin 54 on the sliding member 36 and has an ovalopening 66 in which the eccentric 44 engages. By turning the wheel 48,the cursor can thus be moved across the base I 6.

The manner in which the device functions is best explained by means of apractical example of its use.

Let is be assumed, for example, that it is required to determine whatdepth of water there will be at a particular point on a given chart at1400 hours on a particular day.. The chart ,4 indicates a sounding of 8feet at that point; the Nautical Almanack gives the time of high wateras 1200 hours, the days height of tide as 24 ft., the spring rise as 30ft. and the duration of tide rise or fall as 6 hours.

As already' explained, the ldifference between the spring rise (30 ft.)and the days height of tide (24 ft.) gives the height at low Water abovelow water ordinary spring tide, i. e. 6 ft.

At 1400 hrs. the tide will be falling. The pointer I2 is therefore setso that its line B falls from a point on the scale a2 (Fig. 2)representing high water (24 ft.) to a point on the scale al (Fig. 2)representing loW Water (6 ft.). This is done by manipulation of the twopins 25 and 29, the cursor D being placed successively along theleft-hand edge and the right-hand edge of the frame and the pointerbeing set against the appropriate markings on its scale and taking upthe position shown in Fig. 3.

The cursor is then moved so that its line 40 coincides with the 4 hoursdivision on the 6-hou1' line of the time scale, the time (1400 hrs.) atwhich the height of Water is required being 2 hours after the time ofhigh water or 4 hours before the time of low water. The cursor is shownin that position in Fig. 3 and, as will be seen, its scale isintersected by the line B at a height of 191/2 feet.

The height of Water above datum (low water ordinary spring tide) at thepoint and time in question will, therefore, be 191/2 feet and, in orderto ascertain the depth of water, it is necessary only to add thesounding of 8 feet. Thus, the depth is 271/2 feet.

It Will be realised that the Whole operation has been effected by makingone simple subtraction to ascertain the height of low water and onesimple addition to ascertain the nally required depth of water.

The device shown in Figs. 3-6 can be varied in many ways. Thus, the timescale could be arranged on the cursor D at the side of, instead ofabove, the pointer so that the device would be as shown diagrammaticallyin Fig. '7 to which the same references have been applied as to Fig. 2.In this case the low water scale A is secured on the frame I0 and thehigh water scale A2 is on the right hand edge of the cursor. An indexline b is arranged on the transparent cover of the frame above thecursor. In using the device, the line B is set against the low and highwater values on the scales A' and A2 respectively, while the cursor ispositioned at the left of the frame; the cursor is then moved to theright so that the appropriate time on the time scale is in register withthe index line b and the registered height of water is then indicated bythe intersection of the line B with the scale A2.

1t will be understood that many departures can be made from thearrangements described above. Thus, in the case of Figs. 3-6 the pointercould be arranged so as to be set by many diiierent forms of mechanism,a notable example being quick pitch screws. The pointer I2 having a lineB on it could be replaced by a straight-edge as could the upper part 32of the cursor. Conversely, the lower part 34 of the cursor could be madetransparent and have a line marked on it to serve as the index line.

1t will also be understood that the device in accordance with theinvention can be used for other purposes than that of determining thedepth of water at a particular point and a particular time. Obviously,it could be used for the 5 converse problem of determining the time atwhich there will be a particular depth of water.

We claim:

1. A device for evaluating data relating to tides comprising a frame. aiirst linearly divided scale xed in said frame, a second linearly dvidedscale mounted in said frame parallel with said first scale, means formoving said second scale towards and away from said rst scale, a pivotmounted in said frame between said scales, means for moving said pivotparallel to said scales, index means carried by said pivot and providinga straight index line intersecting said scales, means for turning saidindex means about said pivot, a set of harmonically divided scalesparallel to each other and at right angles to said linearly dividedscales and index means providing a straight index line intersecting saidharmonically divided scales, said harmonically divided scales and saidlast mentioned index means being mounted for relative movement by saidmeans for moving said second linearly divided scale.

2. A device as claimed in claim 1 in which said harmonically dividedscales are iixed in said frame and said last mentioned index means aremovable with said second linearly divided scale.

3. A device as claimed in claim l in which said last mentioned indexmeans is fixed in said frame and said harmonically divided scales aremovable with said second linearly divided scale.

HENRY ERNEST LLOYD OWEN. ROBERT ELIAS LLOYD OWEN.

REFERENCES CITED The following references are of record in the le ofthis patent:

